I think if you can manage to get hired on as full-time by the VA, then you do get a pretty nice retirement package. But as someone else noted, they hire a lot of physicians as contractors at less than 100% full-time.
However...even if you only work part-time for the VA, you are still entitled to enroll in their federal health insurance benefit plan, which is a major perk. (You can enroll your dependents too.) I know a couple of attendings who are mostly private practice now, but continue to see pts at the VA for as little as one half-day per week, in order to keep their good VA health benefits.
Don't know if I could keep working at the VA, personally...even for good health insurance...